Genes that are growth factor inducible and which themselves encode transcriptional factors are likely to play important roles in regulating cell growth. We have recently identified one such gene, EGR1, which in addition is: a) modulated during normal myeloid differentiation; and b) maps to human chromosome 5q23-5q31. These data suggest that EGR1 may play a critical role in cell growth and tumorigenesis in general and in myeloid differentiation in particular. We intend to explore this hypothesis by defining the cell lineage(s) in which EGR1 expression normally occurs, identifying changes in expression patterns and gene structure in cells of patients with secondary AML and attempting gene transfer studies in the promyelocytic leukemia cell line HL60 and fibroblasts to examine if either growth or differentiation can be affected by overexpressing EGR1 or by inhibiting its activity.